Valley photonic crystals (PCs) play a crucial role in controlling light flow and
realizing robust nanophotonic devices. In this study, rotated gradient valley PCs
are proposed to realize topological rainbow trapping. A topological rainbow is
observed despite the presence of pillars of different shapes, which indicates the
remarkable universality of the design. Then, the loss is introduced to explore the
topological rainbow trapping of the non-Hermitian valley PC. For the step-angle
structure, the same or different losses can be applied, which does not affect the
formed topological rainbow trapping. For a single-angle structure, the applied
progressive loss can also achieve rainbow trapping. The rainbow is robust and
topologically protected in both Hermitian and non-Hermitian cases, which is
confirmed by the introduction of perturbations and defects. The proposed
method in the current study presents an intriguing step for light control and
potential applications in optical buffering and frequency routing.